Optical detector

Abstract

A technique includes using at least one emitter to generate a first optical signal to propagate along a first optical path to interact with a target, to generate a second optical signal and generate a third optical signal to propagate along a second optical path other than the first optical path to generate a fourth optical signal. The technique includes using at least one receiver to acquire a first measurement of the second optical signal and acquire a second measurement of the fourth optical signal. The technique includes generating an indication of a parameter that is associated with a target, which includes scaling a ratio of the first and second measurements based at least in part on optical communication between the emitter(s) and the receiver(s) that does not involve interaction with the target.

What is claimed is:  
     
       1. A method comprising:
 using at least one emitter to generate a first optical signal to propagate along a first optical path to interact with a target to generate a second optical signal and generate a third optical signal to propagate along a second optical path to generate a fourth optical signal; 
 using at least one receiver to acquire a first measurement of the second optical signal and acquire a second measurement of the fourth optical signal; and 
 generating an indication of a parameter associated with the target, the generating comprising scaling a first ratio of the first and second measurements based at least in part on optical communication between the at least one emitter and the at least one receiver that does not involve interaction with the target. 
 
     
     
       2. The method of  claim 1 , wherein
 the one emitter comprises a first emitter and a second emitter; 
 at least one receiver comprises a first receiver; 
 the generating further comprises determining a second ratio of a first measurement of optical crosstalk communication between the first emitter and the first receiver to a second measurement of optical crosstalk communication between the second emitter and the first receiver; and 
 the scaling further comprises determining a third ratio of the first ratio to the second ratio. 
 
     
     
       3. The method of  claim 1 , wherein
 the at least one emitter comprises a first emitter; 
 the at least one receiver comprises a first receiver and a second receiver, 
 the generating further comprises determining a second ratio of a first measurement of optical crosstalk communication between the first emitter and the first receiver to a second measurement of optical crosstalk communication between the first emitter and the second receiver; and 
 the scaling further comprises determining a third ratio of the first ratio to the second ratio. 
 
     
     
       4. The method of  claim 1 , wherein
 the parameter comprises a particle density of the target or a distance to the target. 
 
     
     
       5. The method of  claim 1 , wherein the optical communication comprises an optical crosstalk communication. 
     
     
       6. The method of  claim 1 , wherein the generating further comprises comparing the scaled first ratio to a threshold to generate the indication of the parameter. 
     
     
       7. The method of  claim 1 , wherein
 the at least one emitter comprises a first emitter and a second emitter; 
 the at least one receiver comprises a first receiver; and 
 the generating is further based on a first measure of indirect and direct crosstalk communication between the first emitter and the first receiver and a second measure of indirect and direct crosstalk communication between the second emitter and the first receiver. 
 
     
     
       8. The method of  claim 1 , wherein
 the at least one emitter comprises a first emitter; 
 the at least one receiver comprises a first receiver and a second receiver; and 
 the generating is further based on a first measure of indirect and direct crosstalk communication between the first emitter and the first receiver and a second measure of indirect and direct crosstalk communication between the first emitter and the second receiver. 
 
     
     
       9. The method of  claim 1 , further comprising storing in the optical detector at least one calibration value associated with the optical communication that does not involve interaction with the target. 
     
     
       10. An optical detector comprising:
 at least one emitter to:
 generate a first optical signal to propagate along a first optical path to interact with an object to generate a second optical signal; and 
 generate a third optical signal to propagate along a second optical path other than the first optical path to generate a fourth optical signal; 
 
 at least one receiver to:
 acquire a first measurement of the second optical signal; and 
 acquire a second measurement of the fourth optical signal; and 
 
 a controller to scale a first ratio of the first and second measurements based at least in part on at least one additional measurement acquired by the at least one receiver which does not involve interaction with the object to generate an indication of a parameter associated with the object. 
 
     
     
       11. The optical detector of  claim 10 , wherein the controller is adapted to compare the scaled first ratio to a threshold to generate the indication. 
     
     
       12. The optical detector of  claim 10 , wherein
 the controller is adapted to scale the first ratio based on a second ratio of measurements acquired by the at least one receiver in the absence of the object. 
 
     
     
       13. The optical detector of  claim 12 , wherein the controller is adapted to store data indicative of the second ratio. 
     
     
       14. The optical detector of  claim 10 , wherein
 the parameter comprises a particle density of the target or a distance to the object. 
 
     
     
       15. The optical detector of  claim 10 , wherein at least one additional measurement comprises a measurement of optical crosstalk communication between the at least one receiver and the at least one emitter. 
     
     
       16. An apparatus comprising:
 an integrated circuit comprising:
 a controller; 
 at least one driver adapted to use at least one emitter to generate at least one electrical signal to:
 generate a first optical signal to propagate along a first optical path to interact with an object to generate a second optical signal; and 
 generate a third optical signal to propagate along a second optical path other than the first optical path to generate a fourth optical signal; and 
 
 at least one receiver adapted to receive at least one electrical signal indicative of a first measurement of the second optical signal and a second measurement of the fourth optical signal, 
 
 wherein the controller is adapted to scale a first ratio of the first and second measurements based at least in part on optical crosstalk communication between the at least one emitter and the at least one receiver to generate an indication of a parameter associated with the object. 
 
     
     
       17. The apparatus of  claim 16 , wherein
 the parameter comprises a particle density of the object or a distance to the object. 
 
     
     
       18. The apparatus of  claim 16 , wherein optical crosstalk communication comprises at least one of an indirect optical communication between the at least one emitter and the at least one receiver in the absence of the object and a direct optical communication between the at least one receiver and the at least one emitter in the absence of the object. 
     
     
       19. The apparatus of  claim 16 , wherein
 the at least one emitter comprises a first emitter; 
 the at least one receiver comprises a first receiver and a second receiver; and the controller is adapted to:
 determine a second ratio of a first measurement of optical crosstalk communication between the first emitter and the first receiver to a second measurement of optical crosstalk communication between the first emitter and the second receiver; and 
 
 determine a third ratio of the first ratio to the second ratio to scale the first ratio. 
 
     
     
       20. The apparatus of  claim 16 , wherein
 the least one driver is adapted to drive a first emitter to generate the first optical signal and drive a second emitter to generate the third optical signal; and 
 the receive path is adapted to:
 receive a first electrical signal generated in response to optical energy sensed by an optical receiver and indicative of the first measurement of the second optical signal; and 
 receive a second electrical signal generated in response to optical energy sensed by the optical receiver and indicative of the second measurement of the fourth optical signal.